U.S. patent application number 13/040612 was filed with the patent office on 2012-09-06 for light conversion module and light source system including the same.
This patent application is currently assigned to HC PHOTONICS CORP.. Invention is credited to MING HSIEN CHOU, YING HAO SU.
Application Number | 20120224252 13/040612 |
Document ID | / |
Family ID | 46753138 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120224252 |
Kind Code |
A1 |
CHOU; MING HSIEN ; et
al. |
September 6, 2012 |
LIGHT CONVERSION MODULE AND LIGHT SOURCE SYSTEM INCLUDING THE
SAME
Abstract
A light conversion module includes a coupler for combining two
light beams to form a combined light beam, a nonlinear crystal
arranged to receive the combined light beam and configured to
include a plurality of poling regions for performing successive
nonlinear frequency mixing processes, a first optical device
configured to focus the combined light beam onto the nonlinear
crystal, a first moving stage carrying the nonlinear crystal and
moving the nonlinear crystal for an adjustment of a focus position
of the combined light beam on the nonlinear crystal, and an optical
detector configured for measuring a power level of the light beam
from the nonlinear crystal for the adjustment of the focus position
of the combined light beam on the nonlinear crystal.
Inventors: |
CHOU; MING HSIEN; (HSINCHU,
TW) ; SU; YING HAO; (HSINCHU, TW) |
Assignee: |
HC PHOTONICS CORP.
HSINCHU
TW
|
Family ID: |
46753138 |
Appl. No.: |
13/040612 |
Filed: |
March 4, 2011 |
Current U.S.
Class: |
359/328 ;
359/326 |
Current CPC
Class: |
G02F 1/3501 20130101;
G02F 1/3558 20130101; G02F 1/3532 20130101; G02F 2001/3546
20130101 |
Class at
Publication: |
359/328 ;
359/326 |
International
Class: |
G02F 1/37 20060101
G02F001/37; G02F 1/35 20060101 G02F001/35 |
Claims
1. A light conversion module, comprising: a coupler combining two
light beams to form a combined light beam; a nonlinear crystal
arranged to receive the combined light beam, configured to include
a plurality of poling regions for performing successive nonlinear
frequency mixing processes; a first optical device configured to
focus the combined light beam onto the nonlinear crystal; a first
moving stage carrying the nonlinear crystal and configured for
moving the nonlinear crystal for an adjustment of a focus position
of the combined light beam on the nonlinear crystal; and an optical
detector configured for measuring a power level of a light beam
from the nonlinear crystal for the adjustment of the focus position
of the combined light beam on the nonlinear crystal.
2. The light conversion module of claim 1, further comprising a
splitting mirror for directing a portion of the light beam to the
optical detector.
3. The light conversion module of claim 1, further comprising a
second optical device for focusing the light beam from the
nonlinear crystal and a second moving stage carrying the second
optical device for adjusting a focus point of the second optical
device.
4. The light conversion module of claim 1, wherein the nonlinear
crystal comprises a first poling region for a sum frequency
generation process, a second poling region for a second harmonic
generation process, and a third poling region for a sum frequency
generation process, wherein the first, second, and third poling
regions are arranged in a cascading manner.
5. The light conversion module of claim 4, wherein the first poling
region includes a poling spatial period in a range of from 11 to 13
micrometers, the second poling region includes a poling spatial
period in a range of from 6 to 8 micrometers, and the third poling
region includes a poling spatial period in a range of from 4 to 5
micrometers.
6. The light conversion module of claim 4, wherein the first and
second poling regions are separated by a distance of 6 micrometers
to 2 millimeters, and the second and third poling regions are
separated by a distance of from 4 micrometers to 2 millimeters.
7. The light conversion module of claim 1, further comprising a
heating element for heating the nonlinear crystal.
8. The light conversion module of claim 1, further comprising a
temperature sensor adjacent to the nonlinear crystal for
controlling the temperature of the nonlinear crystal.
9. The light conversion module of claim 1, further comprising a
position sensor for sensing a position of the first moving
stage.
10. The light conversion module of claim 1, further comprising a
housing containing at least the nonlinear crystal and a
communication port disposed on the housing.
11. A light source system, comprising: a first laser source
producing a first light beam with a first near-infrared wavelength;
a second laser source producing a second light beam with a second
near-infrared wavelength; and a light conversion module comprising:
a coupler combining the first and second light beams to form a
combined light beam; a nonlinear crystal arranged to receive the
combined light beam, configured to include a plurality of poling
regions for performing successive nonlinear frequency mixing
processes to provide a light beam including red, green, and blue
wavelengths; a first optical device configured to focus the
combined light beam onto the nonlinear crystal; a first moving
stage carrying the nonlinear crystal and configured for moving the
nonlinear crystal for an adjustment of a focus position of the
combined light beam on the nonlinear crystal; and an optical
detector configured for measuring a power level of a light beam
from the nonlinear crystal for the adjustment of the focus position
of the combined light beam on the nonlinear crystal.
12. The light source system of claim 11, further comprising a
splitting mirror for directing a portion of the light beam from the
nonlinear crystal to the optical detector.
13. The light source system of claim 11, further comprising a
second optical device for focusing the light beam from the
nonlinear crystal and a second moving stage carrying the second
optical device for adjusting a focus point of the second optical
device.
14. The light source system of claim 11, wherein the nonlinear
crystal comprises a first poling region for a sum frequency
generation process, a second poling region for a second harmonic
generation process, and a third poling region for a sum frequency
generation process, wherein the first, second, and third poling
regions are arranged in a cascading manner.
15. The light source system of claim 14, wherein the first poling
region includes a poling spatial period in a range of from 11 to 13
micrometers, the second poling region includes a poling spatial
period in a range of from 6 to 8 micrometers, and the third poling
region includes a poling spatial period in a range of from 4 to 5
micrometers.
16. The light source system of claim 15, wherein the first and
second poling regions are separated by a distance of 6 micrometers
to 2 millimeters, and the second and third poling regions are
separated by a distance of from 4 micrometers to 2 millimeters.
17. The light source system of claim 11, further comprising a
heating element for heating the nonlinear crystal.
18. The light source system of claim 11, further comprising a
temperature sensor adjacent to the nonlinear crystal for
controlling the temperature of the nonlinear crystal.
19. The light source system of claim 11, further comprising a
position sensor for sensing a position of the first moving
stage.
20. The light source system of claim 11, further comprising a
processing device storing a predetermined power level and
configured to compare the power level of the light beam from the
nonlinear crystal and the predetermined power level.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a light source system, and
relates more particularly to a light source system employing a
nonlinear crystal.
[0003] 2. Description of the Related Art
[0004] Existing lasers do not provide lights with wavelengths
covering the entire desired optical spectrum. Nonlinear crystals
can be coupled to existing lasers to double the frequency of a
laser, to sum or subtract the frequencies of two different lasers
to produce a third frequency, or to parametrically generate a new
frequency. As such, lights with wavelengths other than those of
lights from existing lasers can be generated.
[0005] The frequency conversion processes include second harmonic
generation, sum frequency generation (SFG), and
difference-frequency generation (DFG). In the process of second
harmonic generation (SHG), an incident beam at frequency .omega. is
converted to radiation at the second harmonic frequency 2.omega..
In the process of sum-frequency generation (SFG), light with a
frequency that is the sum of two other frequencies is generated. In
the process of difference-frequency generation, light with a
frequency that is the difference between two other frequencies is
generated.
[0006] An RGB laser radiation source for generating red, green, and
blue light beams using the above frequency conversion processes is
disclosed in U.S. patent application Ser. No. 09/775,208. As shown
in FIG. 1, the RGB laser radiation source includes a first laser
radiation source 1 emitting a first beam with a wavelength of 1064
nm, which is partially frequency-doubled by SHG.sub.1 to generate
green light with a wavelength of 532 nm and is partially directed
to SFM.sub.1. A second laser radiation source 2 produces a second
beam with a wavelength of 1550 nm, which is partially supplied to
the SFM.sub.1 and mixed with the first beam to produce red light
with a wavelength of 632 nm. SHG.sub.2 receives a portion of the
second beam to generate a beam with a wavelength of 780 nm, which
mixes with a portion of the first beam. The two beams are then
sum-frequency mixed by SFM.sub.2 to generate blue light with a
wavelength of 450 nm. The RGB laser radiation source uses several
nonlinear crystals and two lasers to successfully generate red,
green, and blue light beams. However, the design of such an RGB
laser radiation source is complex and non-compact, and the adoption
of too many nonlinear crystals may also increase the cost.
[0007] FIG. 2 shows another RGB source 10 disclosed in U.S. Pat.
No. 7,489,437. The RGB source 10 has a wavelength conversion system
20 including a single NLO (nonlinear optical) unit 22 consisting of
an optical parametric oscillator (OPO), which has a single
periodically poled crystal 26 and is surrounded by input end-mirror
28I and output end-mirror 28O. A fiber-only laser 16 is used to
provide light beam BN, which is converted by a non-linear optical
process to generate red, green, and blue beams BR, BG, and BB. The
OPO is usually configured to be singly resonant at an MIR idler
wavelength. The input end-mirror 28I is antireflection (AR) coated
at the wavelength of the light beam BN and high-reflection (HR)
coated at red, green, blue, and MIR idler wavelengths. Likewise,
the output end-mirror 28O is HR coated at the MIR idler wavelength
and the wavelength of the light beam BN and is AR coated at red,
green and blue wavelengths. The RGB source 10 needs to be built
with high precision so that high conversion efficiency can be
achieved. The RGB source 10 has a complex structure and is not
easily built. In addition, the RGB source 10 uses expensive coated
mirrors. Thus, it is expensive and not a suitable RGB source for
consumer products.
SUMMARY OF THE INVENTION
[0008] One aspect of the present invention is to provide a system
for producing light with a plurality of wavelengths, which has a
capability of adjusting the focus of a light beam on a nonlinear
crystal to achieve a maximum power output.
[0009] One aspect of the present invention is to provide a system,
which can be coupled with two laser sources such that the system
can provide an output light beam with a broad wavelength
distribution.
[0010] In accordance with the above aspects, the present invention
proposes a light conversion module. The light conversion module
comprises a coupler, a nonlinear crystal, a first optical device, a
first moving stage, and an optical detector. The coupler is for
combining two light beams to form a combined light beam. The
nonlinear crystal is arranged to receive the combined light beam
and is configured to include a plurality of poling regions for
performing successive nonlinear frequency mixing processes. The
first optical device is configured to focus the combined light beam
onto the nonlinear crystal. The first moving stage carries the
nonlinear crystal and is configured for moving the nonlinear
crystal for an adjustment of a focus position of the combined light
beam on the nonlinear crystal. The optical detector is configured
for measuring a power level of a light beam from the nonlinear
crystal for the adjustment of the focus position of the combined
light beam on the nonlinear crystal.
[0011] The present invention proposes a light source system, which
comprises a first laser source, a second laser source, and the
above-mentioned light conversion module. The first laser source
produces a first light beam with a first near-infrared wavelength.
The second laser source produces a second light beam with a second
near-infrared wavelength. The coupler of the light conversion
module combines the first and second light beams to form a combined
light beam.
[0012] To better understand the above-described objectives,
characteristics and advantages of the present invention,
embodiments, with reference to the drawings, are provided for
detailed explanations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will be described according to the appended
drawings in which:
[0014] FIG. 1 shows a conventional RGB laser radiation source in
the related art;
[0015] FIG. 2 shows another conventional RGB source in the related
art;
[0016] FIG. 3 is a perspective view showing a light source system
for producing light with a plurality of wavelengths including red,
green and blue wavelengths according to one embodiment of the
present invention;
[0017] FIG. 4 illustrates the light conversion module of a light
source system according to one embodiment of the present invention;
and
[0018] FIG. 5 is a view showing a nonlinear crystal according to
one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] FIG. 3 is a perspective view showing a light source system 3
for producing light with a plurality of wavelengths including red,
green and blue wavelengths according to one embodiment of the
present invention. Referring to FIG. 3, the light source system 3
includes a light conversion module 31, two laser sources 32 and 33,
and a processing device 34. The laser sources 32 and 33 supply two
light beams transmitting through respective optical fibers 35 and
36 into the light conversion module 31, wherein the two light beams
are frequency-mixed to generate a single light beam 4 including
wavelengths ranging from 360 to 760 nm. The two laser sources 32
and 33 may emit light beams of different fundamental wavelengths,
for example, in the infrared wavelength region. One of the laser
sources 32 and 33 can be, for example, a mode-locked Nd:YAG
solid-state laser emitting a light beam with a wavelength
.lamda..sub.1 of 1064 nm and having a pulse width of 4 ps at a
pulse repetition frequency of 120 MHz. Another of the laser sources
32 and 33 can be a mode-locked Erbium-based fiber laser, may emit a
light beam with a wavelength .lamda..sub.2 of 1550 nm, and can have
a pulse width of 4 ps at a pulse repetition frequency of 120
MHz.
[0020] FIG. 4 illustrates the light conversion module 31 of a light
source system 3 according to one embodiment of the present
invention. Referring to FIGS. 3 and 4, two laser sources 32 and 33
are optically coupled to a coupler 312 for combining the light
beams with different fundamental wavelengths from the two laser
sources 32 and 33 to generate a combined light beam 5. A first
optical device 314 having, for example, two lenses is optically
coupled to the coupler 312, focusing the combined light beam 5 onto
a nonlinear crystal 316 to achieve high conversion efficiency.
[0021] FIG. 5 is a view showing a nonlinear crystal 316 according
to one embodiment of the present invention. The nonlinear crystal
316 is configured to include a plurality of poling regions for
performing successive nonlinear frequency mixing processes so as to
provide a third light beam including at least three new
wavelengths, for example, red, green and blue wavelengths. In one
embodiment, the plurality of poling regions comprise a first poling
region 3161 configured for performing a sum frequency generation
(SFG) process, a second poling region 3162 for performing a second
harmonic generation (SHG) process, and a third poling region 3163
configured for performing a sum frequency generation (SFG) process.
The first, second, and third poling regions 3161-3163 can be
arranged in a cascading manner. The first poling region 3161 is
used to generate red light (with a wavelength of 630.9 nm) with a
frequency that is the sum of the frequency of the light beam with a
wavelength .lamda..sub.1 of 1064 nm and the frequency of the light
beam with a wavelength .lamda..sub.2 of 1550 nm; the second poling
region 3162 is used to double the frequency of the light beam with
a wavelength .lamda..sub.1 of 1064 nm to generate a green light
with a wavelength of 532 nm; the third poling region 3163 is used
to generate blue light (with a wavelength of 448.4 nm) with a
frequency that is the sum of the frequency of the light beam with a
wavelength .lamda..sub.2 of 1550 nm and the frequency of the red
light with a wavelength of 630.9 nm. Consequently, the light beam 6
from the nonlinear crystal 316 may include red, green, and blue
light.
[0022] In one embodiment, the first poling region 3161 can have a
poling spatial period p1 selected from a range of from 11 to 13
micrometers. The second poling region 3162 can have a poling
spatial period p2 selected from a range of from 6 to 8 micrometers.
The third poling region 3163 can have a poling spatial period p3
selected from a range of from 4 to 5 micrometers. In addition, the
first, second, and third poling regions 3161 to 3163 can be
separated from each other. The three poling regions 3161 to 3163
can be separated by an equal distance or by different distances.
For example, the first poling region 3161 and the second poling
region 3162 can be separated by a distance L.sub.1 of approximately
from 6 micrometers to 2 millimeters. The second poling region 3162
and the third poling region 3163 can be separated by a distance
L.sub.2 of approximately from 4 micrometers to 2 millimeters.
[0023] As shown in FIG. 4, the nonlinear crystal 316 is placed on a
temperature-regulating member 320 for heating. The
temperature-regulating member 320 may be, for example, a metal
plate. The temperature-regulating member 320 can include a heating
element 3212 and a temperature sensor 3214 for regulating the
temperature of the temperature-regulating member 320. The
temperature sensor 3214 and the heating element 3212 can be
connected to a temperature controller 326 configured to regulate
the temperature of the nonlinear crystal 316. As show in FIG. 3,
the light conversion module 31 can include a housing 311 at least
enclosing the heating element 3212 and the temperature sensor 3214,
all of which constitute a regulated oven for containing the
nonlinear crystal 316 and regulating the temperature of the
nonlinear crystal 316.
[0024] In one embodiment, the temperature controller 326 can be
electrically coupled to a processing device 34 to allow the
temperature controller 326 to be externally controlled.
[0025] A first moving stage 322 is provided to carry the nonlinear
crystal 316, configured to move relative to the focal point of the
combined beam 5 along a direction indicated by 318. With the
adjustment of the location of the first moving stage 322, the focal
point of the combined beam 5 can be incident on a proper location
so that maximum conversion efficiency can be achieved.
[0026] In one embodiment, a position sensor 324 can be disposed to
sense the position of the first moving stage 322. The first moving
stage 322 and the position sensor 324 can be electrically coupled
to a stage controller 328. The position sensor 324 generates a
position feedback signal to the stage controller 328, which
supplies a control signal to the first moving stage 322 in
accordance with the position feedback signal, driving the first
moving stage 322 to a desired position.
[0027] Referring to FIG. 4 again, the light conversion module 31
may comprise a second optical device 332 for focusing the light
beam 6 from the nonlinear crystal 316. The second optical device
332 can be carried by a stage 336 electrically coupled to a stage
controller 330 and moving along the travel path of the light beam 6
for adjusting the focus point of the second optical device 332. The
stage controller 330 can be electrically coupled to the processing
device 34, which supplies control signals to the stage controller
330.
[0028] As shown in FIG. 4, in order to drive the stage 322 to a
proper position to allow the maximum power level of the light beam
6 from the nonlinear crystal 316 to be achieved, an optical
detector 338 is provided in the light conversion module 31 to
measure the power level of the light beam 6, to which a required
control signal is generated and supplied to the stage 322 in
response. A splitting mirror 334 is used to split the light beam 6;
a portion of light is directed to the optical detector 338 and
another portion of light beam 6 transmits through the splitting
mirror 334 to the exterior of the light conversion module 31. The
optical detector 338 is electrically coupled to the processing
device 34 configured for analyzing detected signals to determine
where the stage 322 should move to so that the maximum power level
of the light beam 6 can be obtained. In accordance with computing
results, the processing device 34 sends a command to the stage
controller 328, which drives the moving stage 322 to a desired
position.
[0029] In one embodiment, the processing device 34 stores a
predetermined power level. The processing device 34 compares a
detected power level with the predetermined power level,
determining the movement of the moving stage 322, and sends a
command to the stage controller 328 to drive the moving stage 322
to the position where the power level of the light beam 6 is
approximately equal to the predetermined power level.
[0030] In one embodiment, the light conversion module 31 may
further comprise a communication port (not shown) disposed on the
housing 311 for connecting the light conversion module 31 and the
processing device 34. The communication port may be one of a serial
COM port, a parallel port, a USB port, a Firewire port, a TCP/IP
port, and a TCP/IP socket. With the establishment of the
communication port, the processing device 34 can be independent
from the light conversion module 31. In addition, the independent
processing device 34 can further include a plug-and-play circuit
such that the processing device 34 can detect the connection of the
communication port with the processing device 34, automatically
loading necessary drivers.
[0031] The light conversion module 31 is simple and uses fewer
components. All components can be contained in the housing 311,
shown as enclosed by a dashed line box in FIGS. 3 and 4. Thus, the
light conversion module 31 can be very compact and suitable for
portable consumer products. The light conversion module 31 does not
need to be built with high precision. In addition, the light
conversion module 31 is capable of automatically adjusting the
power level of the emitted light beam to the optimum power
level.
[0032] The above-described embodiments of the present invention are
intended to be illustrative only. Numerous alternative embodiments
may be devised by persons skilled in the art without departing from
the scope of the following claims.
* * * * *